Chemical elements
  Tungsten
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      Tungsten Hexafluoride
      Tungsten Oxyfluorides
      Tungsten Dichloride
      Double Chlorides of Trivalent Tungsten
      Tungsten Tetrachloride
      Tungsten Pentachloride
      Tungsten Hexachloride
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      Metatungstic Acid
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      Calcium Metatungstate
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      Mercurous Metatungstate
      Nickel Metatungstate
      Potassium Metatungstate
      Rubidium Metatungstate
      Samarium Metatungstate
      Silver Metatungstate
      Sodium Metatungstate
      Strontium Metatungstate
      Thallous Metatungstate
      Zinc Metatungstate
      Pertungstic Acid
      Tungsten Bronzes
      Potassium Tungsten Bronze
      Lithium Tungsten Bronze
      Lithium Potassium Tungsten Bronze
      Sodium tungsten bronzes
      Tungsten Disulphide
      Tungsten Trisulphide
      Thiotungstates
      Tungsten Diselenide
      Tungsten Triselenide
      Tungsten Phosphides
      Tungsten Diphosphide
      Tritungsten Tetraphosphide
      Tungsten Monophosphide
      Tungsten Subphosphide
      Phosphotungstic Acids
      12-Tungstophosphoric Acid
      11-Tungstophosphates
      21:2-Tungstophosphoric Acid
      10-Tungstophosphoric Acid
      9-Tungstophosphoric Acid
      17:2-Tungstophosphates
      3-Tungstophosphates
      Hypophosphotungstates
      Tungsten Diarsenide
      Tungsten Chloro-arsenide
      12-Tungsto-arsenates
      11-Tungsto-arsenates
      9-Tungsto-arsenic Acid
      17:2-Tungsto-arsenates
      Tungsto-arsenites
      Tritungsten Carbide
      Ditungsten Carbide
      Tungsten Monocarbide
      Tungsten Iron Carbides
      Tungstocyanic Acid
      Ammonium Tungstocyanide
      Calcium Tungstocyanide
      Cadmium Tungstocyanide
      Caesium Tungstocyanide
      Lead Tungstocyanide
      Magnesium Tungstocyanide
      Manganese Tungstocyanide
      Potassium Tungstocyanide
      Rubidium Tungstocyanide
      Silver Tungstocyanide
      Sodium Tungstocyanide
      Strontium Tungstocyanide
      Thallium Tungstocyanide
      Zinc Tungstocyanide
      Tungsticyanic Acid
      Tungsten Sesquisilicide
      Tungsten Disilicide
      Tungsten Trisilicide
      12-Tungstosilicic Acid
      Iso-12-tungstosilicic Acid
      10-Tungstosilicates
      Tungsten Boride
      12-Tungstoboric Acid
      Iso-12-tungstoboric Acid
    Alloys
    PDB 1aor-2rav
    PDB 2rb5-6fit

Cadmium Tungstocyanide, Cd2[W(CN)8]






Cadmium Tungstocyanide, Cd2[W(CN)8].8H2O, may be prepared from the silver salt by double decomposition, or by the following method due to Rosenheim and Dehn. A solution of 12-tungstosilicic acid in concentrated hydrochloric acid is reduced electrolytically until the solution becomes greenish yellow in colour. Strong alkali is added to remove the excess of acid, and solid potassium cyanide is then added in considerable quantity. On evaporation of this solution, potassium chloride separates. A similar solution may be obtained more directly by treating the compound K3W2Cl9 with potassium cyanide. The solution is now treated with a concentrated solution of cadmium sulphate and digested on the water-bath; an impure cadmium salt separates which is dissolved in concentrated ammonia solution, and the solution, placed in a freezing mixture, is saturated with ammonia. Cadmiumtriammine tungstocyanide, [Cd(NH3)3]2[W(CN)8].2H2O, separates in long golden-yellow needles, which on washing with water, or on exposure to air, lose ammonia and yield the corresponding diammine salt, [Cd(NH3)2]2[W(CN)8].2H2O. On treatment with 1 to 2 per cent, sulphuric acid, microscopic yellow prisms of cadmium tungstocyanide, Cd2[W(CN)8].8H2O, are obtained. When exposed to sunlight the crystals turn red but no change in weight occurs, and on heating, the yellow colour returns. When heated to 125° C. 7 molecules of water are lost. The salt is only slightly soluble in water, but is more readily soluble in hydrochloric acid.

The cadmium salt may also be obtained from the pyridine compound W(OH)2(SCN)3.2C5H5N. which dissolves in potassium cyanide solution, forming a blue solution which turns yellow on warming and can be made to yield the above-mentioned triammine salt.


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